Regarding the charge control-type inkjet printer related to the present invention, the abstract of Patent Document 1 describes, as a solution for easily determining an optimal nozzle driving electric voltage for forming ink particles without skill, “the controlling unit does not energize a deflection electrode until the ink particles enter a gutter after giving an electric charge to the ink particles from an electrically charged electrode, arbitrarily set a plurality of times of nozzle driving electric voltages, and gives an electrical charge to the ink particles by an optional electrically charged electric voltage. The amount of the electric charge given to the ink particles is detected by a sensor for the amount of the electric charge, and when the electrically charged electric voltage is proportional to the amount of the electric charge of the ink particles, it is determined to be normal, and the central value of the nozzle driving electric voltage within a range where it is determined to be normal is set as the nozzle driving voltage used for printing.”